1. Field of Invention
This invention relates to clutches for motor vehicles and, in particular, to an improved design and use of a frictional ring rather than conventional frictional linings in automotive clutches.
2. Brief Statement of the Prior Art
The typical automotive clutch has a clutch disc fixedly secured to the drive shaft and supported between the flywheel and a pressure plate. The clutch cover, which is bolted onto the flywheel includes a conical (Belleville) spring that is actuated by a clutch throw out mechanism and hydraulics to release the Belleville spring force against the pressure plate, clamping the clutch disc between the pressure plate and flywheel. The clutch disc has a marcel, which is a segmented wave washer usually formed of separate segments riveted to the clutch disc which support frictional linings on its opposite sides. The clutch linings typically have a high frictional coefficient material, usually an organic composite laminated to a metal annular ring and are riveted to the marcel. The marcel provides smooth clutch engagement by imparting a progressive, rather than abrupt, disc engagement.
The most commonly used frictional linings are organic composite linings which are molded or bonded to a metal support ring, and drilled with a preselected pattern of holes to receive rivets which secure the assembly of the linings to the opposite sides of the marcel. Metal support rings are preferred with conventional engineering wisdom, on the theory that the metal ring enhances heat transfer from the linings, and because the metal ring provides the necessary strength to take the hoop stresses placed on the linings at high speeds of revolution. Because the torque loads which are imposed on the linings are very substantial and because all the torque load is received in shear loads on the rivets, many rivets are required to secure the typical assembly of linings to the marcel and clutch disc. The large number of rivets reduces the frictional surface area of the linings. Manufacturing and servicing of clutches is also costly, and a significant factor is the machining, parts and assembly time required to place and fasten the many rivets used to secure the facings to the marcel.
There have been many improvements in materials and designs for clutch discs, including the replacement of asbestos-containing facings with organic composite linings or metallic linings, to avoid potential health hazards to the public. All the designs, however, have continued to use a conventional lining, which as mentioned above, is formed with a support ring, usually of metal, to which is bonded a material of high frictional characteristics.
There exists, today, a need for a simple and efficient frictional member for use in an otherwise conventional automotive clutch. Ideally, the frictional member will be an integral or monolithic member with its opposite faces engaging the pressure ring and flywheel, thereby avoiding the costly machining and assembly of frictional linings to a marcel or clutch disc.